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Super X11QPL User's Manual
When the following screen appears, select Yes to confirm that the selected device is to be
used as a journaling drive. The options are Yes and No.
Note: RAID Write Hole (RWH) is a condition associated with a power/drive-failure/crash
while writing to a RAID5 volume. The use of journaling drive that contains partial parity
logging (PPL) can reduce the potential data loss. Refer to the following illustration for
the use of journaling drive.
Journaling
Drive
(PPL)
Store PPL to the journaling drive
RAID SW for Read-modify-write Case
(read) old data
XOR operation
(write) new data
Disk1
Disk2
(Data)
(Data)
Partial parity logging (PPL) = old data XOR old parity
New parity = new data XOR PPL
172
(read) old parity
XOR operation
(write) new parity
Disk3
Disk4
(Data)
(Parity)
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